Technical Field
The present invention relates to a data reading method, and more particularly, to a data reading method for a rewritable non-volatile memory, a memory controlling circuit unit, and a memory storage device.
Description of Related Art
The markets of digital cameras, cellular phones, and MP3 players have expanded rapidly in recent years, resulting in escalated demand for storage media by consumers. The characteristics of data non-volatility, low power consumption, and compact size make a rewritable non-volatile memory module (e.g., a flash memory) ideal to be built in the portable multi-media devices as cited above.
Generally, data written to the rewritable non-volatile memory module is encoded according to an error correcting code, and data read from the rewritable non-volatile memory module is also decoded through a corresponding procedure. However, a correcting capability of the error correcting code has its limit. For example, when the error correcting code is implemented by using a turbo code algorithm or a low density parity code algorithm in an iterative manner, as the number of times for performing an iteration decoding reaches a specific number of times, a phenomenon where the number of error bits is not reduced with increases in the number of times for performing the iteration decoding may occur in the subsequent process of the iteration decoding. This phenomenon is also known as the error floor. Accordingly, it is one of the major subjects in the industry as how to successfully decode the read data in order to obtain original data.
Nothing herein should be construed as an admission of knowledge in the prior art of any portion of the present invention. Furthermore, citation or identification of any document in this application is not an admission that such document is available as prior art to the present invention, or that any reference forms a part of the common general knowledge in the art.